Disclosed is a process for the generation of arylamine compounds. More specifically, illustrated herein are methods for bisformylating arylamines for synthesizing arylamine which can be incorporated into photoconductive imaging members as hole transport components.
Arylamines can be selected as hole transport molecules in organic photoconductors. Examples of arylamine hole transport molecules include a siloxane-containing hole transport molecule illustrated with reference to Compound I:
wherein R1, R2, R3 R4, R5, R6, and R7, independently represent an alkyl or hydrocarbon radical of for example 1 to about 20 carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, stearyl, and higher analogs thereof.
Processes for preparing Compound I wherein R1–R6, are hydrocarbon radicals and more specifically where R2 and R6 are methyl, ethyl or isopropyl may be lengthy and involve reagents that may be considered not “environmentally friendly.” For example, processes for preparing Compound I may entail as many as six distinct synthetic manipulations with up to 30 days to complete such manipulations, including a Vilsmeier reaction for the bisformylation of an intermediate Compound II (N,N-diphenyl-4-aminobiphenyl) to its bisformylated form.

The Vilsmeier reaction can be used to introduce aldehyde or formyl groups onto an aromatic ring to yield a formylated-aryl moiety. An example Vilsmeier reaction entails the formation of a Vilsmeier reagent which may be formed by reacting N,N-dimethylformamide (DMF) with phosphorous oxychloride (POCl3), phosgene (COCl2) or thionylchloride (SOC12) of which phosphorous oxychloride is preferred. The preparation of the Vilsmeier reagent is normally done in-situ. The Vilsmeier reagent then reacts with the aromatic ring of an activated molecule such as a phenol or aromatic amine. The introduction of such a group into a generic triarylamine is shown as the reaction sequence below:

Compound II may be bisformylated by way of a Vilsmeier reaction as illustrated herein after. While monoformylation of Compound II may be achieved with relative ease by way of a Vilmeier reaction, bisformylation may be more difficult and may require that the reaction be accomplished at elevated temperatures of from about 90° C. to about 110° C., temperatures above the decomposition of the Vilsmeier reagent (Td˜81° C.). Another disadvantage to bisformylation of Compound II by the Vilsmeier reaction is that the reagents such as phosphorous oxychloride used in such a process may be considered to be hazardous and toxic.
